The present invention is directed to preparation of cobalt containing complexes and their use to improve hydroesterification reactions.
Hydroesterification involves the reaction of an olefinic compound, CO and an alcohol in the presence of a suitable catalyst, to produce ester generally at elevated temperatures and pressures. Cobalt carbonyl and cobalt compounds, such as organic and inorganic salts of cobalt, are most commonly used catalysts. Representative hydroesterification processes are disclosed in U.S. Pat. Nos. 2,542,767; 2,689,261; and 2,768,968. Use of pyridine promoters and/or hydrogen to improve the rate of such cobalt catalyzed hydroesterification reactions is also known; see U.S. Pat. No. 3,507,891; A. Matsuda and H. Uchida, Bull. Chem. Soc. Japan, 38, 710, (1965); V. Gankin, N. Gordina, M. Katsnelson, D. Rudkovskii, Zh. Pr. K., 40, 1862, (1967).
When cobalt carbonyl is used as the catalyst component, no induction period is required for the hydroesterification reaction to begin after the reactants and catalyst component have been charged and the reaction temperature is reached. Cobalt carbonyl, however, is expensive and requires special handling procedures. When other less expensive cobalt compounds, such as cobalt salts, are used as catalyst components, an induction period is required before the hydroesterification reaction begins. This induction period can be substantial, especially where high molecular weight olefinic reactants are used. Addition of hydrogen to cobalt salt catalyzed hydroesterification is known to reduce the induction period; however, the addition of hydrogen results in the formation of undesirable aldehyde-type by-products.
It has been discovered that cobalt complexes can be prepared by reacting cobalt compounds with carbon monoxide, hydrogen, a pyridine, and an alkanol; and that these complexes can be used to catalyze the hydroesterification reaction without requiring any induction period and without causing undesirable by-product aldehyde formation.